Tree
of life proposal divides scientists

A ROSE is a rose -- but it may not belong to the family
Rosaceae forever.

In a highly controversial plan that could
shake biology to its core, a few maverick biologists are proposing to
abandon the traditional way of naming and ranking every living thing on
Earth, a system invented 250 years ago by the Swedish botanist Carolus
Linnaeus and a staple of textbooks to this day.

It was
a good system for its time, critics say, invaluable for describing how
one organism arose from another and how creatures as big as whales, as
tiny as germs and as self-important as people are related.

Kingdom, phylum, class, order, family, genus and species -- the
traditional hierarchy has been memorized by generations of students with
the help of phrases such as King Philip Came Only For Gold and Silver.

But now, critics argue, the system is swamped by the sheer volume of
information pouring in from genetic studies, which are rearranging the
branches and twigs of the tree of life at a dizzying rate.

They
say there are simply not enough ranks in the traditional system to
encompass this growth spurt. In place of Linnaeus' creation, they want a
family tree without ranks, as free-form and flowing as evolution
itself.

``I think it's the greatest thing since sliced bread,''
said Michael Donoghue, director of the Harvard University herbaria and a
proponent of the new scheme. ``It's the beginning wave of something
that's probably going to happen -- and people aren't going to like
it.''

Which appears, at this point, to be an understatement.

``It's moronic!'' said William Burger, curator of botany for the Field
Museum in Chicago, expressing the sentiment of a great many of his
colleagues at the recent International Botanical Congress in St.
Louis.

``When you've got a system that's worked for 200 years,''
he said, ``who the hell cares about the phylogeny of these plants?''

Phylogeny?

It's a fancy word for evolutionary relationships, and
it's the heart and soul of biological classification.

When
Linnaeus began his ambitious work of classifying everything in the
animal, vegetable and mineral kingdoms in the 1700s, Charles Darwin's
theory of evolution was still a century away, and each type of living
thing was thought to have been separately created.

Linnaeus
divided the animal and plant kingdoms into classes, and then again into
genera and species, based on the superficial characteristics of organisms
-- say, whether the reproductive organs of a flower were out in the open
or hidden.

As more species were discovered, scientists were forced
to add more categories to the Linnaean hierarchy, and they changed it to
reflect what they knew about evolutionary relationships.

So, for
instance, in the current version the human lineage goes this way:

Single-celled creatures called eucaryotes gave rise to metazoans, the
multicelled animals. Metazoans begat chordates, which have rods of
cartilage supporting the nerves that run along their backs. And they in
turn spawned animals with backbones, four-legged animals, mammals,
primates, hominids, early humans and us.

In the language of
classification, we belong to the Eukarya, the Metazoa, the phylum
Chordata, subphylum Vertebrata, superclass Tetrapoda, class Mammalia,
order Primates, family Hominidae, genus Homo and species Homo
sapiens.

But as the tree of life gets more complicated,
researchers continue to discover new and interesting groupings that they
want to formally name so they can communicate more easily among
themselves.

Convention invention

They
invent new categories -- things such as tribes, cohorts and phalanxes,
not to mention supertribes, subcohorts and infraphalanxes -- and wedge
them in among the traditional ones.

In theory this can expand the
system indefinitely. But in practice it becomes awkward and confusing.

The beauty of the new, rankless nomenclature is that ``you don't have to
spend time memorizing whether an infracohort is higher than a
subcohort,'' said Kathleen Kron, a botanist at Wake Forest University.
``You can concentrate on evolution and biology and the whole reason we
got into this in the first place.''

One of the leading proponents
of the new system, known as phylogenetic nomenclature, is Brent Mishler,
director of the herbaria at the University of California-Berkeley.

He points out that the family tree for the 300,000 species of green
plants alone, if printed out on a very wide roll of computer paper, would
be nearly one and a half miles long. On that tree are hundreds of
thousands of branching points, each one giving rise to a group of plants
that scientists might like to name.

But under today's rules, you
can't give a group a formal name without assigning it a rank, too.

And the thought of trying to squeeze all those ranks into the Linnaean
system makes Mishler shake his head.

``There's just no way,'' he
said. ``You get rid of the ranks. If you're an educated biologist, you
just need to know how these (groups) nest inside each other'' -- and that
information is widely available in databases that contain diagrams of
groups branching off from other groups, like the branches and twigs of a
tree.

Under the new system, researchers would be free to name any
branch of the tree of life without regard to rank.

But they
wouldn't rename existing groups -- ``far from it,'' said Kevin de
Queiroz, curator of the national collection of reptiles and amphibians at
the Smithsonian Institution. ``We're probably using all the same names
and giving them different definitions. So we would still be Mammalia. We
just wouldn't care if it was a class or a superclass or a
giga-superclass.''

Mishler goes further than most in overhauling
the new system, arguing that even the category of species should be
abolished. Instead, each organism would go by a single name --
sapiens,in our case. If more than one creature bore the
same moniker -- as in the many species labeled alba (meaning
white), vulgaris (common) or californicus (from California)
-- you simply append the name of the next group up the line, like a
schoolteacher distinguishing two Jennifers by attaching their last
initials.

Others would keep the idea of species, either with their
current names or with slight changes, so humans might become
Homo/sapiens or Homo-sapiens, reminiscent of the hyphenated
names some people take after marriage.

Which is appropriate,
because the whole idea makes a lot of people crazy and has some talking
in terms of divorce, so deep is the split between advocates of the old
system and the proposed new one.

``It looks great when all you see
is a theoretical concept on the board,'' said Barbara Ertter, collections
manager at the UC-Berkeley herbaria. ``But I rejected it on the grounds
that it's going to screw up a system that is working.''

Dick
Brummitt, a botanist at the Royal Botanic Gardens in Kew, England, adds
that if some researchers want to use the new system, ``it's not for me to
stop them. But if they think other people are going to stop using
traditional names, they're mistaken. The great majority are totally
against what these people are trying to do.''

Opponents fear that
a new system would lead to chaos: With two separate types of names
floating around, they say, biologists would have difficulty searching
through past studies for things that are relevant to their work.
Herbaria, those repositories of plant specimens, might have to relabel
their collections at great expense.

Given these potential
drawbacks, many scientists feel themselves uncomfortably straddling the
fence. They can see the logic of the new way of thinking. But they fear
that without some sort of ranking it will be much more difficult to
communicate, in words, the relationships between the organisms they're
studying.

``In practical work, as opposed to theoretical work, one
has to come to grips with what has already been done and put it into some
kind of framework,'' said Malcolm McKenna of the American Museum of
Natural History in New York, who recently co-authored a book classifying
all the mammals. ``I find myself trying to accommodate both worlds.''

Mixed
emotions

David Maddison, a specialist in
the evolution of beetles at the University of Arizona and one of the
creators of the Tree of Life Web page, admits, ``I haven't decided
personally what I'm gonna do the next time I get around to doing some
classifications.''

Proponents of the new nomenclature are now
engaged in writing rules, which will be known as the PhyloCode. It will
take them a few years yet.

They acknowledge that they may never
win over the senior scientists who sit on the committees that determine
the rules of nomenclature for various fields of biology. But they are
convinced that the next generation of leaders, who grew up with computers
and are comfortable with the idea that a diagram can supersede words,
will take to the new method and make it their own.

And if the new
code does not succeed -- well, that would be nothing less than the
survival of the fittest at work.

``We're almost counting on the
older generation of people to be resistant. That's the way it works,''
said de Queiroz of the Smithsonian. ``That's not necessarily a bad thing.
It keeps crazy ideas from spreading too quickly.''

It's a sort of
natural selection, he said. If people find the new system is handier than
the old, ``it will succeed and replace the other one. If it doesn't, it
won't. That's how we prefer it to be.''